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Biochemical insights into the alleviated inhibition on nitrogen metabolism by micro-and nano-plastics at the biocathode of bioelectrochemical systems
Summary
A lab study investigated how microplastics and nanoplastics inhibit nitrogen removal (denitrification) at the biological cathode of a bioelectrochemical treatment system, and found that adding algal biochar largely reversed this inhibition, increasing nitrate removal from 51% to 76%. This is relevant for wastewater treatment, suggesting that biochar amendments could protect microbial treatment processes from the disrupting effects of microplastic contamination in sewage.
In this work, the inhibition of microplastics (MPs, 50 μm) and nanoplastics (NPs, 50 nm) on denitrification at biocathode in bioelectrochemical system (BES), and the alleviated of this inhibition on nitrogen metabolism using algal biochar (ABC) were investigated. With the addition of biochar, it was found that nitrate removal increased to 75.6 % in the NP-50-ABC group, significantly higher than the 51.2 % observed in the NP-50 group. First, biochar was found to mitigate oxidative stress by reducing reactive oxygen species (ROS) and lactate dehydrogenase (LDH) release, while maintaining extracellular polymer secretion and cell membrane integrity. Second, ABC also helped reshape microbial communities, enrich denitrifying bacteria, and enhance the abundance of key functional genes (napA, napB, norB, nosZ) and enzymes. Third, biochar stimulated pathways for the anabolic reduction of nitrate to ammonia, thereby synergistically removing nitrate through denitrification. These findings provide theoretical support for improving BES resilience against emerging pollutants.